Method and apparatus for accessing a wireless communication system

• US 20050286465A1
• Filed: 03/02/2005
• Published: 12/29/2005
• Est. Priority Date: 06/24/2004
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Zhuang, Xiangyang
• Granted Patent: US 7,599,327 B2
• Time in Patent Office: Days
• US Class Current: 370/329
• CPC Class Codes: H04L 25/0212 of impulse response
• CPC Class Codes: H04L 25/022 of frequency response
• CPC Class Codes: H04L 25/0226 sounding signals per se
• CPC Class Codes: H04L 25/0228 with direct estimation from sounding signals
• CPC Class Codes: H04L 27/2607 Cyclic extensions
• CPC Class Codes: H04L 27/2613 Structure of the reference signals
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT

Abstract

Access to a wireless communication system (100) by a subscriber station (101-103) is facilitated by selecting (705) an access sequence from a set of sequences that have been identified to have a low average of peak-to-average-power-ratios of access signals generated by the set of sequences and also based on a good cross-correlation of the access signals; forming (714) the access waveform by generating an access signal using the access sequence and appending in the time domain a cyclic prefix to the access signal; and transmitting (715) the access waveform. In some implementations, the access waveform is cyclically shifted (820) before the cyclic prefix is appended, and in some implementations, the signal is transmitted (710, 810) in a randomly selected sub-band of an access interval.

Claims

1. A method used by a subscriber station in a wireless communication system for accessing the communication system, comprising:

selecting an access sequence from a set of N_c access sequences that have been identified to have a low average of peak-to-average-power-ratios of access signals generated by the set of N_c access sequences and to have good cross-correlation of the access signals generated by the set of N_c access sequences, and wherein the set of N_c access sequences has been generated by a corresponding set of sequences of length K, wherein K is a quantity of sub-carriers identified for transmitting an access signal;

forming the access waveform by generating an access signal using the access sequence and appending in the time domain a cyclic prefix to the access signal; and

transmitting the access waveform.

2. The method according to claim 1, wherein the access signal is generated by performing an Inverse Fast Fourier Transform on a frequency domain sequence formed from the access sequence.

3. The method according to claim 1, further comprising selecting at random a frequency sub-band having K sub-carriers from among N_b1 sub-bands.

4. The method according to claim 1, wherein the selection of the access sequence from the set of N_c access sequences is made as a random selection among the N_c access sequences.

5. The method according to claim 1, wherein the low average of the peak-to-average-power-ratios of the entire set of N_c access signal is less than 6 dB.

6. The method according to claim 1, wherein the good cross-correlation of the access signal generated by the set of N_c access sequences is when the absolute correlation values at all lags of the cross correlation between any sequence pair are evenly distributed such that the maximum absolute correlation value over all lags is no more than two times the average of the absolute correlation values.

7. The method according to claim 1, wherein the corresponding set of sequences of length K is based on a set of (N_G−

1) Generalized Chirp Like (GCL) sequences that are defined as;

8. The method according to claim 7, wherein when N_G is larger than K, the corresponding set of sequences of length K is generated by truncating the set of GCL sequences to length K.

9. The method according to claim 7, wherein when N_G is smaller than K, the corresponding set of sequences of length K is generated by copying (K−

N_G) terms from the beginning of each GCL sequence and appending them to the end.

10. The method according to claim 1, wherein the corresponding set of sequences of length K is generated by a random phase shift keyed sequence or a Golay phase shift keyed sequence.

11. The method according to claim 1, further comprising cyclically time shifting the access signal by a shift value that is one of a defined set of N_sh shift values.

12. The method according to claim 1 wherein the length of the cyclic prefix appended to the access signal in the time domain is determined based on the maximum timing difference among all possible subscriber locations and the excessive delay spread of the channel in the deployment environment.

13. The method according to claim 1 wherein the accessing of the communication system is by one of a random transmission and an assigned uplink transmission.

14. A method used by a subscriber station in a wireless communication system for accessing the communication system, comprising:

selecting an access sequence from a set of N_c access sequences;

generating an access signal using the selected access sequence;

cyclically time shifting the generated access signal by a shift value that is one of a defined set of N_sh shift values;

forming an access waveform by appending a cyclic prefix to the selected access waveform; and

transmitting the access waveform.

15. The method according to claim 14, wherein the number of shift values N_sh is determined based on └

N_sp/L_CPe┘

, wherein N_sp is the Fast Fourier Transform size of a special Fast Fourier Transformation window, and L_CPe is a length of an extended cyclic prefix of a special orthogonal frequency division multiplex symbol

16. The method according to claim 14, wherein the number of shift values N_sh is determined based on └

N_sp/L_CP┘

, wherein N_sp is the Fast Fourier Transform size of a special Fast Fourier Transformation window, and L_CP is determined based on an excessive delay spread of the channels encountered in a deployment.

17. The method according to claim 14, further comprising selecting at random a frequency sub-band having K sub-carriers from among N_b1 sub-bands.

18. The method according to claim 14 wherein the accessing of the communication system is one of a random transmission and an assigned uplink transmission.

19. A method used by a base station in a wireless communication system for facilitating an access of the communication system by a subscriber station comprising:

identifying in a transmitted control signal one or more sub-bands in an access interval, each of which comprises K sub-carriers and for which each of the sub-bands is available for a subscriber station to use to transmit an access signal;

receiving an access signal from the subscriber station in one of the one or more sub-bands during the access interval; and

.

analyzing the access signal to identify at least one of a cyclic shift of a defined set of cyclic shifts and an access sequence of a set of access sequences.

20. The method according to claim 19, further comprising processing the access signal to extract subscriber station synchronization information.

21. The method according to claim 20, wherein the subscriber station synchronization information is at least one of timing, power, frequency offset, and channel impulse response.

22. The method according to claim 19 wherein the access of the communication system is by one of a random transmission and an assigned uplink transmission.